Typing-extensions

- Fix importing `typing_extensions` on Python 3.7.0 and 3.7.1. Original
patch by Nikita Sobolev (sobolevn).

- Runtime support for PEP 646, adding `typing_extensions.TypeVarTuple`
and `typing_extensions.Unpack`.
- Add interaction of `Required` and `NotRequired` with `__required_keys__`,
`__optional_keys__` and `get_type_hints()`. Patch by David Cabot (d-k-bo).
- Runtime support for PEP 675 and `typing_extensions.LiteralString`.
- Add `Never` and `assert_never`. Backport from bpo-46475.
- `ParamSpec` args and kwargs are now equal to themselves. Backport from
bpo-46676. Patch by Gregory Beauregard (GBeauregard).
- Add `reveal_type`. Backport from bpo-46414.
- Runtime support for PEP 681 and `typing_extensions.dataclass_transform`.
- `Annotated` can now wrap `ClassVar` and `Final`. Backport from
bpo-46491. Patch by Gregory Beauregard (GBeauregard).
- Add missed `Required` and `NotRequired` to `__all__`. Patch by
Yuri Karabas (uriyyo).
- The `final` decorator now sets the `__final__` attribute on the
decorated object to allow runtime introspection. Backport from
bpo-46342.
- Add `is_typeddict`. Patch by Chris Moradi (chrismoradi) and James
Hilton-Balfe (Gobot1234).

- Fix broken sdist in release 4.0.0. Patch by Adam Turner (AA-Turner).
- Fix equality comparison for `Required` and `NotRequired`. Patch by
Jelle Zijlstra (jellezijlstra).
- Fix usage of `Self` as a type argument. Patch by Chris Wesseling
(CharString) and James Hilton-Balfe (Gobot1234).

The following non-exported but non-private names have been removed as they are
unneeded for supporting Python 3.6 and newer.

- TypingMeta
- OLD_GENERICS
- SUBS_TREE
- HAVE_ANNOTATED
- HAVE_PROTOCOLS
- V_co
- VT_co

Previous releases

Prior to release 4.0.0 we did not provide a changelog. Please check
the Git history for details.